Continuously variable drivetrain

ABSTRACT

Drivetrains and frames for vehicles, equipment, machines, etc. Some embodiments of the drivetrains and frames are particularly suited for human powered machines, such as bicycles and exercise equipment. In some embodiments, a drivetrain includes a reciprocating crank coupled to a crank pivot. A lever couples to the crank via a lever pivot positioned on the crank. A lever stop cooperates with a lever guide surface to guide a motion of the lever as the lever pivots about the lever pivot. The lever and/or the crank are operably coupled to a drive pulley, idler pulley, and/or compound pulley. In some embodiments, a drive cable operably couples the lever and/or the crank to the drive pulley, idler pulley, and/or the compound pulley. In one embodiment, one or more pulleys couple to the lever&#39;s distal ends. In some embodiments, the drivetrain includes a wheel hub adapted to receive torque from the crank via a drive pulley.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/747,068, filed on May 10, 2007, which claims priority to U.S.Provisional Patent Application 60/799,601, filed on May 11, 2006. Theentire disclosure of each of the above applications is herebyincorporated by reference in its entirety.

This Application is related to U.S. patent application Ser. No. ______Attorney Docket No. LINEARB.031C2, U.S. patent application Ser. No.______, Attorney Docket No. LINEARB.031C3, U.S. patent application Ser.No. ______, Attorney Docket No. LINEARB.031C4, U.S. patent applicationSer. No. ______, Attorney Docket No. LINEARB.031C5, U.S. patentapplication Ser. No. ______, Attorney Docket No. LINEARB.031C6, U.S.patent application Ser. No. ______, Attorney Docket No. LINEARB.031C7,U.S. patent application Ser. No. ______, Attorney Docket No.LINEARB.031C8, and U.S. patent application Ser. No. ______, AttorneyDocket No. LINEARB.031C9, all filed on even date and which are herebyincorporated by reference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to mechanical power transmissionsystems and more specifically to continuously variable drivetrains.

2. Related Art

Pulley and belt systems used to transmit mechanical energy are verycommon and have been used extensively in industry for decades. Theirbenefits of low cost, reliability, modularity, and high efficiency havecreated thousands of applications. Typically, two pulleys are used,although three, four, five, or more pulleys may be employed. Generallyone belt or cable is used, although systems with multiple belts are notuncommon, such as those used in automobiles. With these systems, two ormore pulleys have two or more annular grooves that are designed toaccommodate two or more belts. Pulleys can be made from steel, aluminum,plastic, and other materials. The material choice is often determined bythe amount of power to be transferred. Pulleys come in many differentsizes, ranging from miniature pulleys with a diameter of less than 10millimeters to very large pulleys over a meter in diameter. Belts aremade from many different materials, but all of them are flexible. Often,a rubber belt is used with embedded steel strands to increase strength.Other common materials used in belt construction are urethane, neoprene,steel, and composites. The belt profile can be round, V shaped, flat,grooved, or other shapes. Timing belts use a series of tooth shapedridges which engage corresponding indentations in a pulley to maximizepower transfer and eliminate slip. Some belts employ grooves to allowthem to wrap around smaller diameter pulleys.

Most pulley and belt drivetrains are endless, which means that theytransfer power rotationally from one pulley to another. The pulleys arerigidly attached to rotating drive and driven shafts and a circular beltrotates endlessly in a closed loop. Idler pulleys are frequently used tocreate and maintain tension on the belt to prevent slippage andpremature failure. Idler pulleys do not transfer power and typicallyemploy a bearing in the bore of the pulley to minimize friction andincrease life. The bearing and idler pulley assembly is often pressedover a non-rotating shaft.

Reciprocating pulley and belt, or cable, drivetrains are often found inhuman powered systems. Exercise equipment frequently uses a cable thatis attached to weights at one end and to a bar or other device which aperson can push or pull. The weight is lifted and then returned to itsresting state. An idler pulley is generally suspended at a height abovethe weights. This lifting and lowering of the weight createsreciprocating motion of the cable and pulley. Similarly, exercisemachines such as those simulating the motion of climbing stairs can usesimilar reciprocating pulley and cable drivetrains. All of thesedrivetrains suffer from a loss of kinetic energy at the end of eachstroke. For example, in a bicep curl, the human grasps a bar with bothhands and lifts the bar to a position near the chest, and then returnsit to the resting state. Kinetic energy is created during movement ofthe bar and then lost when the movement is stopped at the end of thestroke. Some exercise machines, including Nautilus type equipment,employ a cam which causes the weights to move more rapidly at the end ofthe stroke. This effect creates more efficient exercise by minimizingthe loss of kinetic energy. The exercise is also more efficient becauseit becomes more difficult as the muscle contracts. During contractionthe mechanical advantage of a muscle increases and it becomes morepowerful. As the muscle position changes and creates a larger mechanicaladvantage, with cam or Nautilus type equipment, the weightsimultaneously becomes more difficult to lift.

Linear drive systems in human powered vehicles have been attempted manytimes. However, they are not as efficient as commonly used drivetrains,such as sprocket and chain systems used on bicycles, due to the loss ofkinetic energy at the end of each stroke. Many of the human poweredlinear drive systems are also complex, and each gear, bearing, pulley,cable, chain, or sprocket used in the drivetrain reduces efficiency. Thecomplex systems are also heavy, and weight is a significant factor inhuman powered vehicles because it increases inertia and powerrequirements. Complex systems are also more expensive and more prone tobreaking.

The most common human powered vehicle is a bicycle. A bicycle uses asprocket and chain drivetrain which very efficiently transfers humanpower to the rear wheel. However, power is only efficiently createdthrough about 60 degrees of the stroke, and only becomes very efficientfor about 30 degrees of the 360 degree rotary stroke. This stroke alsocreates two large torque spikes per revolution. In order to reducestress on the body (especially the knees), and minimize fatigue, a highpedaling speed is required to achieve high efficiency. This highpedaling speed reduces the torque spikes and also creates momentum tocarry the pedals through the power phase of the stroke. However, themajority of people are not comfortable pedaling at a high speed andconsequently do not maintain a cadence which maximizes the efficiencyinherent in a bicycle's rotary stroke.

Further, the most common complaint from individuals riding bicycles isdiscomfort created by the bike seat. This discomfort is significantenough to keep many people from riding bikes, and to reduce thefrequency that others use their bicycles. Recent studies showing thatbicycle riding contributes to impotence and other health problemsaggravate the discomfort problem caused from bike seats. However,maximizing the efficiency inherent in the bicycle drivetrain requiresthat the user stay seated while pedaling. This position is moreconducive to a higher cadence and expends less of the user's energy.Riding a bicycle seated creates a situation where most of the user'sweight is on the seat, and thus prevents the majority of the user'sweight from being applied to the pedals. This loss in force can only beregained by pedaling at high speed, where there is a corresponding dropin torque and less force needs to be applied to the pedals to maintainan efficient power output.

The second most common complaint among bicycle users is difficulty whenshifting. While this is rarely a problem with avid cyclists, infrequentusers routinely shift in the wrong direction, shifting to a higher gearwhen starting up a hill, or vice versa. This problem can lead to thechain coming off of a sprocket, binding of the chain, a broken chain,and in rare cases the user getting injured in a fall. The problemfrustrates enough people that it reduces the percentage of thepopulation that ride a bicycle.

There exists a need for a human powered drivetrain that eliminates thetorque spike inherent in a bicycle drivetrain and that allows lowerspeed, efficient pedaling at a cadence comfortable for the majority ofpeople. There also exists a need for a linear drivetrain that minimizesor eliminates the loss of kinetic energy at the end of each stroke.There exists a need for a simple, inexpensive, lightweight, andefficient linear drivetrain that can be altered to accommodate differentuser sizes and preferences. Additionally, there exists a need for humanpowered vehicles where discomfort from the seat is eliminated and thatallows most or all of the user's weight to be applied to the pedals.Finally, there exists a need for a drivetrain which eliminates shiftingof the derailleur system used to vary speed and torque on hills.

SUMMARY OF THE INVENTION

The systems and methods herein described have several features, nosingle one of which is solely responsible for its desirable attributes.Without limiting the scope as expressed by the claims that follow, itsmore prominent features will now be discussed briefly. After consideringthis discussion, and particularly after reading the section entitled“Detailed Description of the Preferred Embodiments” one will understandhow the features of the system and methods provide several advantagesover traditional systems and methods.

In one aspect, a pulley and cable drivetrain is disclosed whichcontinuously varies speed and torque throughout its stroke. In somesystems the continuously variable drivetrain incorporates two pedals,which are contacted by a person's feet, and move in reciprocating motionto transmit power. Each pedal attaches to a crank which rotates along anarc defined by a pivot point at an end opposite the pedal. The cranksattach to a frame, which in some systems comprises the support structurefor a human powered vehicle or exercise equipment. Also attached to eachcrank is a pulley, the pulley positioned at a distance from the crankpivot point to produce the correct rotational speed of a drive pulley.The drive pulley, of which there is one for each crank, has a drivecable wrapped around a deep annular groove. The drive cable terminatesat the interior of the drive pulley.

In one aspect the drive cable then travels around a first idler pulleyand at a second end is attached to the frame. A second, dependent cableis used to raise one pedal while the other is depressed. The dependentcable is attached at each end to each of the cranks. The dependent cablethen travels around a second idler pulley which is attached to theframe. The idler pulley is positioned above the cranks so that thedependent cable is tensioned by each crank.

In some applications the continuously variable drivetrain is used inconjunction with human powered vehicles, specifically a bicycle. Thedrivetrain allows the seat to be removed from the bicycle. The userstands on the pedals near the rear of the bicycle and in some aspectsleans forward on a chest support.

In some embodiments the dependent cable and the dependent pulley areeliminated to allow each crank to be operated independently of theother. This allows the user to pedal with one leg, both legssimultaneously, or to vary the starting and ending positions of thestroke. In some such systems, the pedals may utilize a cover whichextends over the top of the foot or fasteners to attach the user's shoesto the pedals.

In some systems the idler pulley is eliminated and the drive cableterminates at and is attached to the crank. This has the effect ofreducing the speed at which the drive pulley rotates. In other systemstwo or more idler pulleys are attached to each crank, which increasesthe speed at which the drive pulley rotates.

In some systems a compound pulley is used to accelerate the ratio changeof the continuously variable drivetrain. The compound pulley, one foreach drive pulley, incorporates two deep annular grooves to accommodatetwo cables. One cable is the drive cable and the second cable is thecompound cable. Depending on whether the stroke is in its power orreturn phase, one cable is unwinding from the compound pulley while theother cable is winding onto the compound pulley.

In another aspect, a compound pulley is attached to each crank, and alever is attached to each crank. The lever is connected to the crankwith a lever pivot, and in one embodiment has lever pulleys attached atboth ends of the lever. A lever cable runs from the compound pulley,around the lever pulleys, and terminates at a strong stationarystructure, such as the frame. The lever contacts a roller, which causesthe lever to swing and pull more cable at the end of the stroke than atthe beginning of the stroke.

One aspect of the invention is directed to a drivetrain having a crankcoupled to a lever pivot, and a lever operably coupled to the crank; thelever is configured to rotate less than 360 degrees about the leverpivot during a power phase of a stroke. Yet another aspect of theinvention concerns a drivetrain having a crank, a pulley attached to thecrank, a lever operably coupled to the crank, and a lever stop operablycoupled to the lever.

A different aspect of the invention relates to a drivetrain thatincludes a lever configured to rotate about an axis during a stroke ofthe drivetrain, the stroke comprising a power phase and a return phase.The drivetrain additionally includes a hook attached to the lever, alever stop configured to cooperate with the lever, and a drive pulleyoperationally coupled to the lever. In some embodiments, the inventionconcerns a drivetrain provided with first and second rotatable cranksand a crank pivot, wherein the cranks are configured to rotate less than180 degrees about the crank pivot during a power phase of a stroke. Thedrivetrain can additionally exhibit first and second lever pivotsattached respectively to the first and second rotatable cranks, andfirst and second levers attached respectively to the first and secondlever pivots, wherein the levers are configured to rotate less than 300degrees during the power phase. The drivetrain, in some cases,additionally includes at least one crank pulley attached to each crank,at least one lever stop operably coupled to each lever, and at least onedrive pulley operably coupled to each crank.

In yet another aspect, the invention is directed to a drivetrainconfigured to convert human power to mechanical propulsive power. Thedrivetrain has a lever configured to rotate less than 360 degrees duringa power phase of a stroke, a hook attached to the lever, and a firstpulley attached to the lever. In other embodiments, the invention coversa drivetrain with two levers and two lever pivots, wherein each leverpivot attaches to a respective lever, and wherein each lever isconfigured to rotate less than 360 degrees about a respective leverpivot during a power phase of a stroke. The drivetrain can also havefirst and second lever pulleys attached to each lever, two compoundpulleys, and two flexible tension members, each flexible membercontacting a respective compound pulley, first lever pulley, and secondlever pulley.

A different aspect of the invention relates to a drivetrain having acrank configured to rotate less than 360 degrees during the power phaseof a stroke, a lever pivot coupled to the crank, and a drive pulleyhaving a spiraling root. In some embodiments, the drivetrain includes aflexible tension member operably coupled to the crank and the drivepulley such that a first end of the flexible tension member terminatesat the root of the drive pulley, the flexible tension member is spirallywound on the drive pulley at the beginning of the power phase, and theflexible tension member unwinds from the drive pulley during the powerphase. Yet one more aspect of the invention concerns a drivetrain havinga crank configured to rotate less than 360 degrees during the powerphase of a stroke, a lever pivot coupled to the crank, and a leveroperably coupled to the crank via the lever pivot; the lever can beconfigured to rotate less than 360 degrees about the lever pivot duringthe power phase.

Still another embodiment of the invention addresses a bicycle havingfirst and second cranks, each crank configured to rotate less than 360degrees during the power phase of a stroke. The bicycle can have firstand second lever pivots coupled, respectively, to the first and secondcranks. In one case, the bicycle additionally includes first and secondlevers operably coupled, respectively, to the first and second cranks,the first and second levers configured to rotate less than 360 degreesabout the first and second lever pivots during the power phase. Thebicycle can also have a frame, wherein the first and second cranksand/or the first and second levers are coupled to the frame. In someembodiments, a front wheel and a rear wheel operably couple to theframe.

One aspect of the invention is directed to a human powered vehiclehaving a frame, at least one wheel attached to the frame, and at leastone crank which is configured to rotate less than 360 degrees during thepower phase of a stroke; the crank is operably coupled to the wheel. Thehuman powered vehicle components are configured such that during thepower phase a rotation of the crank causes a rotation of the wheel, andwherein the power phase is continuously variable and causes the wheel torotate more rapidly at the beginning than at the end of the power phase.

In some embodiments, the invention addresses a continuously variabledrivetrain having first and second foot pedals and first and secondcranks; wherein the first and second foot pedals couple, respectively,to the first and second cranks. The drivetrain can be configured suchthat the cranks are capable of reciprocating motion, and the cranksrotate along an arc defined by a crank pivot point located at an enddistal from the pedals. The drivetrain can further include a frameadapted to support the cranks, and first and second drive pulleyscoupled, respectively, to the first and second cranks. The drivetrainadditionally has first and second crank pulleys coupled, respectively,to the first and second cranks; the crank pulleys can be positioned at adistance from the crank pivot point. In some cases, the drivetrain has afirst drive cable wrapped around the first drive pulley and the firstcrank pulley, and a second drive cable wrapped around the second drivepulley and the second crank pulley.

These and other improvements will become apparent to those skilled inthe art as they read the following detailed description and view theenclosed figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a bicycle utilizing a continuously variabledrivetrain (CVD) and a chest support.

FIG. 2 is a perspective view of the frame and CVD of the bicycle of FIG.1.

FIG. 3 is a perspective view of the chest support of the bicycle of FIG.1.

FIG. 4 is an end view of the support base of the bicycle of FIG. 1.

FIG. 5 is a front perspective view of the frame of the bicycle of FIG.1.

FIG. 6 is a back perspective view of the frame of the bicycle of FIG. 1.

FIG. 7 is a side perspective view of the frame of the bicycle of FIG. 1.

FIG. 8 is a Detail A view of FIG. 7.

FIG. 9 is a side view of the bicycle of FIG. 1 with its front wheelremoved and the chest support folded down.

FIG. 10 is a perspective view of the bicycle of FIG. 1 with its frontwheel removed and the chest support folded down.

FIG. 11 is a perspective view of the CVD of the bicycle of FIG. 1.

FIG. 12 is a second perspective view of the CVD of FIG. 11.

FIG. 13 is a cutaway section view of the hub of the CVD of FIG. 12.

FIG. 14 is a perspective view of a crank of the CVD of FIG. 12.

FIG. 15 is a perspective side view of the drive pulley of the CVD ofFIG. 12.

FIG. 16 is an end view of a drive pulley of the CVD of FIG. 12.

FIG. 17 is a schematic view of a portion of a CVD of FIG. 12 showingcable movement at different locations in a stroke.

FIG. 18 is a second schematic view of a portion of a CVD of FIG. 12showing cable movement at different locations in a stroke.

FIG. 19 is a schematic view of a drive cable at the beginning of astroke.

FIG. 20 is a schematic view of a drive cable at the end of the stroke.

FIG. 21 is a graphical comparison of a stroke of the bicycle of FIG. 1with the stroke of a conventional bicycle.

FIG. 22 is a chart showing stroke torques of the bicycle of FIG. 1 and aconventional bicycle.

FIG. 23 is perspective view of an alternative CVD.

FIG. 24 is a perspective view of yet another alternative CVD.

FIG. 25 is a front view of a pulley used in the CVD of FIG. 24.

FIG. 26 is a perspective view of yet one more alternative CVD.

FIG. 27 is a perspective view of a CVD that can be used in exerciseequipment.

FIG. 28 is a side view of a scooter using a CVD.

FIG. 29 is a side view of yet another alternative CVD.

FIG. 30 is a perspective view of the CVD of FIG. 29.

FIG. 31 is a partially schematic view of the CVD of FIG. 29 at the startof a stroke.

FIG. 32 is a partially schematic view of the CVD of FIG. 29 at themiddle of a stroke.

FIG. 33 is a partially schematic view of the CVD of FIG. 29 at the endof a stroke.

FIG. 34 is a section view of a drive pulley used in the CVD of FIG. 29.

FIG. 35 is a partially schematic view of an alternative CVD at the startof a stroke.

FIG. 36 is a partially schematic view of an alternative CVD at themiddle of a stroke.

FIG. 37 is a partial schematic view of an alternative CVD at the end ofa stroke.

FIG. 38 is a side view of a lever that can be used with the CVD of FIG.29.

FIGS. 39A-39D are schematic views showing contrasting different legpositions of a user operating a conventional bicycle and a CVD.

FIG. 40 is a perspective view of a bicycle and frame that can be usedwith the CVDs disclosed here.

FIG. 41 is a perspective view of yet another bicycle frame that can beused with the CVDs disclosed here.

DETAILED DESCRIPTION OF CERTAIN INVENTIVE EMBODIMENTS

Preferred embodiments of the present invention will now be describedwith reference to the accompanying Figures, wherein like numerals referto like elements throughout. The terminology used in the descriptionpresented herein is intended to be interpreted in its broadestreasonable manner including its specific use herein as well as otheruses in the technical field, even though it is being utilized inconjunction with a detailed description of certain specific preferredembodiments. This is further emphasized below with respect to someparticular terms used herein. Any terminology intended to be interpretedby the reader in any restricted manner that is different than anaccepted plain and ordinary meaning will be expressly and specificallydefined as such in this specification and the descriptions of objects oradvantages associated with certain embodiments is not intended torequire structure fulfilling those objects in all embodiments.

The inventive embodiments disclosed here are related to technologydescribed in U.S. Provisional Patent Application 60/799,601, filed onMay 11, 2006, which is hereby incorporated herein by reference in itsentirety. As used here, the terms “operationally connected,”“operationally coupled”, “operationally linked”, “operably connected”,“operably coupled”, “operably linked,” and like terms, refer to arelationship (mechanical, linkage, coupling, etc.) between elementswhereby operation of one element results in a corresponding, following,or simultaneous operation or actuation of a second element. It is notedthat in using said terms to describe inventive embodiments, specificstructures or mechanisms that link or couple the elements are typicallydescribed. However, unless otherwise specifically stated, when one ofsaid terms is used, the term indicates that the actual linkage orcoupling may take a variety of forms, which in certain instances will beobvious to a person of ordinary skill in the relevant technology.

Components which are used on both the left and right side of a vehicleor equipment are designated with the letters a and b. For example, wherethere are two lever cranks 615, the left lever crank might labeled levercrank 615 a, while the right lever crank might labeled lever crank 615b. Generally, all of the components on a side are designated with theletter a, and all substantially similar components on another side aredesignated with the letter b; when a component is referred togenerically without a side designation, the a or b suffix is removed.

FIGS. 1 and 2 depict a bicycle 100, where the bicycle seat has beenremoved and a chest support 90 added to accommodate a continuouslyvariable drivetrain 10, hereinafter referred to as a CVD 10. The bicycle100 also has a front wheel 80, a fork 86, handlebars 87, a frame 60, anda rear wheel 84, typical of conventional bicycles. The front and rearwheels 80, 84 may use bicycle wheels that are spoked, solid, molded, andany other wheels that can be used for a bicycle. In some embodiments,the fork 86 has two blades which attach to the front axle on each sideof the front wheel 80; however, the fork 86 may also be of single bladestructure. In other embodiments, the fork 86 may be replaced by acomponent that can provide steering of the front wheel 80. Thehandlebars 87 may be constructed of aluminum, steel, carbon fiber, wood,or any other suitable material, and the shape can be modified to suit anindividual user's preference. Referring now to FIGS. 1-3, the chestsupport 90 is comprised of a support 92, which can be foam, aninflatable cushion, netting, or any other material which providessupport for the user's chest. The size, thickness, and shape of thesupport can be modified to suit the user's preferences. To accommodatethe female anatomy, depressions or cups may be formed into the support92. In one embodiment, the support 92 is constructed of foam or otherlightweight flexible material and a firm support structure 93 isattached to the foam on the underside of the support 92. In a preferredembodiment, a support clamp 94 is positioned underneath and attached tothe firm support structure of the support 92. The support clamp 94provides for attachment of the support 92 to the support tube 95. Thesupport clamp 94 also allows the user to tilt the support 92 to optimizethe user's position. The support clamp 94 may be constructed of severaldifferent designs, including traditional methods used to attach and tilta bicycle seat. In one embodiment, the support clamp 94 is plastic andintegrally formed with the support structure 93. The support clamp 94consists of two protrusions 94A extending underneath the support 92,each protrusion 94A having a hole 94B to allow a bolt or quick releaseclamp to be inserted through the holes 94B in the support clamp 94. Thesupport clamp 94 is positioned over the top of a support tube 95, whichhas a support hole 96 integral thereto. In other embodiments, thesupport clamp 94 may use the same design to attach bicycle seats to seatposts. The support tube 95 is positioned between the two protrusions 94Aof the support clamp 94 and the support hole 96 is aligned so that it isconcentric with the holes of the protrusions. The bolt or quick releaseclamp is inserted through one protrusion, through the support hole 96,and through the second protrusion. A nut or clamp can be used to secureand tighten the support 92, to hold it in a preferred position.

Now referring to FIGS. 1-4, the support tube 95 is a cylindrical tubemade from aluminum, titanium, steel, plastic, a composite such as carbonfiber, or any other suitable rigid, strong material. The support tube 95is capable of being raised or lowered so that the height of the support92 can be adjusted to accommodate different users. The support tube 95fits into a hole 91 in a support base 97, the hole 91 having a slightlylarger diameter than the support tube 95. In a preferred embodiment thesupport base 97 at a first end is generally cylindrical to allowinsertion of the support tube 95, and at a second end has an aperture 99with an axis approximately 90 degrees to the axis of the support tube95. At a first generally cylindrical end, the support base 97 has a slot89 to allow a quick release clamp, commonly used in the art, to bepositioned around the first end of the support base 97 and clamp thesupport base 97, and squeeze the support tube 95 firmly, thus holding itin position to prevent movement when the weight of the user's chest ison the support 92.

The aperture 99 is slightly larger than and fits over the frame 60. Theaperture 99 is split on a side below the frame to allow frame fastener98 to fasten securely and rigidly the support base 97 to the frame 60.In one embodiment, the frame fastener 98 has two fastener holes 88 whichextend through both sides of the split in the support base 97, to allowcommon fasteners such as bolts or quick release clamps to be used totighten the frame fastener 98 to the frame 60. The support base 97 canbe moved along the axis of the frame 60 either closer to the front wheel80, or closer to rear wheel 84, to accommodate preferences and sizes ofdifferent users.

Referring now to FIGS. 1, 2, 5-8, and 13, a frame 60 of the bicycle ofFIG. 1 is disclosed. The frame 60 is a structural component, and can beconstructed of steel, aluminum, titanium, beryllium, carbon fiber orother composite, a plastic, such as glass filled nylon, or any othersuitable material. The frame 60 may be composed of two or morematerials. For example, the body of the frame 60 can be made from carbonfiber while the dropouts may be steel. The frame 60 is not subjected tothe loads and stresses of a conventional bicycle frame. Because thebicycle seat is eliminated, there is only a small amount of weight fromthe user distributed to the frame 60. Since the user is standing andleaning forward, most of the user's weight is on pedals 16. The pedals16 ultimately transfer most of the user's weight to the rear axle 33.There is a small amount of weight on the chest support 90, which istransferred to a top tube 62, and ultimately to a head tube 61. Thus theframe 60 can be made significantly lighter than conventional bicycleframes. The head tube 61, a generally cylindrical part of the frame 60,and common in the art, provides for fastening of the fork 86 andsteering of the bicycle 100. Attached to the head tube 61 is the toptube 62, a generally cylindrical tube, typically attached at a first endto the head tube 61 by welding if the frame 60 is metal or plastic. Inone embodiment, the frame 60 is molded from plastic and the top tube 62is integrally formed with the head tube 61. The head tube 61 and toptube 62 may also be joined by gluing, using an epoxy, or other highstrength adhesive. The top tube 62 extends rearward toward the rearwheel 84, and terminates at first and second hinges 64, 65. The hinges64, 65 are composed of strong, rigid tubing such as steel, titanium, oraluminum and provide for folding and storage of the bicycle 100.

Referring to FIGS. 7 and 8, each hinge is comprised of three separatetubes. The middle sections 66 are welded, or permanently attached to thetop tube 62 with adhesive, or the middle sections 66 can be integrallymolded into the top tube 62. The top and bottom sections 67, 68,respectively, are permanently affixed to a back tube 69 using the sameattachment method as the middle section 66. A permanent pin 70 ispermanently inserted into the hinge 64 through the top, middle, andbottom sections 66, 67, 68. The second hinge 65 (not fully shown)utilizes a removable pin 71. The removable pin 71 is inserted into thesecond hinge 65 in the same manner as the permanent pin 70 is insertedinto the first hinge 64. By grasping a handle 72 on the removable pin71, the user may pull and remove the removable pin 71, so that when thefront half of the frame 60 is folded it will pivot on the axis of thepermanent pin 70. In this manner, the frame 60 can be foldedapproximately in half.

Still referring to FIGS. 1, 2, 5-8, and 11, the back tube 69 isdescribed. The back tube 69 is a short, generally cylindrical componentwith approximately the same shape, and made from the same material, asthe top tube 62. The back tube 69 extends rearward in substantially thesame direction as the top tube 62 and terminates at a pulley mount 73.The pulley mount 73, made from the same material as the top tube 62,attaches, protects, and conceals a dependent pulley 24 in a cavity 74within the pulley mount 73, and forms an attachment point for the backtube 69, top stays 76, and down stays 77. A pulley shaft hole 75 is alsoformed in the pulley mount 73, and is a location where a pulley shaft(not shown) is inserted through the top of the pulley shaft hole 75,then through the dependent pulley 24, and finally through the bottom ofthe pulley shaft hole 75. The pulley shaft may be secured with commonfasteners, such as a lock nut or retaining ring, or any other suitablemethod.

Top stays 76 can be integrally formed with the pulley mount 73, or madeseparately and welded, glued, or otherwise bonded to the pulley mount73. In one embodiment the top stays 76, one on the left side and one onthe right side of the frame 60, are made from the same material as therest of the frame 60, although in other embodiments a different materialcan be used. Similarly, the down stays 77 are also attached to thepulley mount 73 at a first end, and can be integrally molded or welded,or glued to the pulley mount 73. The down stays 77, in a preferredembodiment, are made of the same material as the top stays 76. The downstays 77, one on the left side and one on the right side of the frame60, extend down and slightly rearward from the pulley mount 73, and arepositioned on each side of the rear wheel 84. The down stays 77 aregenerally elongated tubes and become wider, or farther apart from eachother and the rear wheel 84, near their second end to allow forattachment of cranks 15. Crank connectors 79 are positioned near thesecond end, near the bottom of the down stays 77, and a crank shaft 14is attached to each crank connector 79, providing for arcuate motion ofthe cranks 15. The cranks 15 are positioned between the rear wheel 84and the crank connectors 79. Joining the down stays 77, slightly aboveand closer to the rear axle 33, are crank stays 78. The crank stays 78,are made from the same material as the down stays 77, and serve tosupport and anchor the cranks 15. The crank stays 78 are generallyelongated tubes that move closer together and closer to the rear wheel84 at a second end near the rear axle 33. The crank stays 78 join thetop stays 76 at a second end near the rear axle 33. Dropouts 63 can beeither attached to the crank stays 78 or molded integrally into thecrank stays 78. In a preferred embodiment, the dropouts 63 areconstructed of steel or aluminum and serve as an attachment point forthe rear axle 33. The rear wheel 84 is positioned between the crankstays 78, the down stays 77, and the top stays 76. The rear axle 33 isattached to the dropouts 63 with standard fasteners such as nuts andwashers.

Referring now to FIGS. 9 and 10, the bicycle 100 can easily be madeportable because the top tube 62 is the only component of the frame 60attaching the front end to the rear end. The down tube, seat tube, andbottom bracket, components of the frame of a conventional bicycle areeliminated. If the front wheel 80 is removed, and the chest support 90is collapsed and rotated down 180 degrees so that it is positionedbetween the frame 60 and the ground or riding surface, the bicycle 100can be quickly folded to a small size. In addition to folding at theaxis of the permanent pin 70, the frame 60 can also be made in twoseparate pieces (not shown) separated at the axis of the pulley shafthole 75. In this configuration, a first section comprised of the headtube 61, the top tube 62, and the pulley mount 73 (the back tube 69 andthe hinges 64, 65 are eliminated) extends to and terminates at thepulley shaft hole 75. A second section begins at the axis of the pulleyshaft hole 75 and extends rearward. The second section is designed tocontact the first section at two areas, one on the left side and one onthe right side of both the first and second sections. The second sectionhas a second pulley shaft hole 75 b formed at the top and bottomconcentric with and outside of the pulley shaft hole 75 on the firstsection. The pulley shaft is inserted first through the top portion ofthe second pulley shaft hole 75 b, then through the top portion of thepulley shaft hole 75, then through the dependent pulley 24, then throughthe bottom portion of the pulley shaft hole 75, and finally through thebottom portion of the second pulley shaft hole 75 b. When the pulleyshaft is removed, the first and second sections of the frame 60separate, splitting the bicycle 100 approximately in half.

Referring to FIGS. 2, 11, 12, and 14, a CVD 10 is disclosed. The CVD 10includes two cranks 15 a, 15 b, which move in reciprocating motion whena user powers the CVD 10. From an original, resting position at thebeginning of a stroke, the movement of the cranks 15 can be defined as apower stroke, which occurs when a crank 15 is depressed by a user, and areturn stroke, which occurs when the crank 15 returns to its originalposition at the beginning of the stroke. In some embodiments, the cranks15 are elongated members which begin with a crank pivot 17 at a firstend, and have a first section 22 which is generally straight. In someembodiments, the crank pivot 17 is a through hole providing forattachment of the crank shaft 14. At a second end the cranks 15 includea pedal mount 18 for attachment of the pedals 16. A second section 19 ofthe crank 15 is designed to position the pedals 16 above the firstsection 22. In some embodiments, the second section 19 is curved upwardso that the cranks 15 can be made from one piece and strength ismaximized. In other embodiments, the second section 19 may extend from10 to 90 degrees, or another angle (for example, 30, 40, 50, 60, 70,80), to the first section 22. The second section 19 may also be weldedto the first section 22, or attached by any other suitable method. Thesecond section 19 serves three functions:

It provides clearance between the user and the frame 60, allowing theuser to pedal higher and at a more favorable angle, thus maximizingpower,

It moves the user forward on the bicycle 100 so that the user's weightis distributed appropriately, and

It lowers a crank pulley 23 so that a more favorable speed ratio isobtained through positioning of the crank pulley 23 relative to a drivepulley 28.

The cranks 15 can be made from aluminum, steel, titanium, plastic, acomposite such as carbon fiber, or another suitable material. The pedals16 can be conventional bike pedals or can be platforms that are weldedor otherwise rigidly attached to the cranks 15. In one embodiment, thepedals 16 are platforms that have limited rotational capability toaccommodate the bending of the legs while a user powers the CVD 10. Thepedals 16 can be made from aluminum, steel, titanium, plastic, acomposite such as carbon fiber, or another suitable material. The userplaces a foot on each pedal 16, and by alternately depressing each pedal16 a, 16 b, delivers power to the CVD 10, which power is thentransferred to a bicycle, scooter, exercise equipment, boat, submarine,plane, or any other human powered device.

Also attached to each crank 15 is the crank pulley 23. In someembodiments the crank pulley 23 is an idler pulley that serves toincrease the speed ratio of the CVD 10. The crank pulley 23 can have anidler bearing 26 inserted into its bore to minimize friction. An idlershaft 27 is inserted through the idler bearing 26 and is then threadedinto a pulley connector 20 to fasten the crank pulley 23 to the crank15. Alternatively, the idler shaft 27 can be pressed into the pulleyconnector 20 or welded, or fastened with other conventional fasteners.In some embodiments the pulley connector 20 is a round through hole, butit can be made with a square, hexagonal, or any other suitable shapedhole. The hole can also be blind, and in some embodiments the idlershaft 27 can be made integral with the crank 15, eliminating the needfor the pulley connector 20.

Also comprising part of the crank 15 are clamp mounts 21, which in apreferred embodiment are through holes located on the first section 22of the crank 15. The clamp mounts 21 can be countersunk so that if ascrew or bolt is used for attachment the heads will be flush with thecrank 15. The clamp mounts 21 allow insertion of fasteners such asscrews, bolts, or pins to provide attachment of cable clamps 29. In someembodiments, the cable clamps 29 are a strong, rigid component made fromsteel although titanium, aluminum, and other materials may be used. Eachcable clamp 29 has two through holes to allow insertion of two machinescrews. In some embodiments, the machine screws are inserted firstthrough the clamp mounts 21, then through a first cable clamp 29A1, andthen threaded into a second cable clamp 29A2. In other embodiments, themachine screws can be first inserted through the second cable clamp29A2. In still other embodiments, only one cable clamp 29A is used and adependent cable 31 is clamped between the crank 15 and the cable clamp29A.

The dependent cable 31 is a flexible tension member that in someembodiments has minimal creep and a break strength greater than themaximum force exerted by the user. The dependent cable 31 can beconstructed of a composite material such as Vectran or Kevlar, but canalso be made from other materials, including steel. A first end of thedependent cable 31 is operably attached to the crank 15 a, and at asecond end it is operably attached to the crank 15 b, with the abovedescribed cable clamps 29. At an area near its midpoint the dependentcable 31 wraps around the dependent pulley 24 so that when the crank 15a is depressed the crank 15 b rises, and vice versa. In one embodiment,the dependent pulley 24 is constructed of aluminum, although steel,plastic (such as glass filled nylon), a composite material, or any othersuitable material can be used. The dependent pulley 24 is an idlerpulley and has a dependent bearing 32 attached at its center to minimizefriction. The dependent pulley 24 is positioned in the cavity 74 of theframe 60 and the pulley shaft (not shown) is inserted through the top ofthe pulley shaft hole 75, through the bore of the dependent bearing 32,and then through the lower portion of the pulley shaft hole 75.

Referring now to FIG. 13, the hub 40 of the CVD 10 is disclosed. The hub40 is comprised of a hub shell 41, a generally cylindrical componentthat contains and protects the one way clutches 42, the torque drivers43, and the rear axle 33. The hub shell 41 can be constructed of steel,aluminum, titanium, carbon fiber or another composite, or any othersuitable material. In some embodiments, the hub shell 41 includes spokeflanges 44, so that the hub shell 41 can be attached to the rear wheel84.

Attached to the hub shell 41 on its inside diameter are one way clutches42. The one way clutches 42 each alternately provide torque to the hubshell 41, rotating the rear wheel 84. In some embodiments the one wayclutches 42 are roller clutches of the type utilizing hardened steelpins circumferentially spaced around the inside diameter of the rollerclutch housing. Hardened steel ramps are positioned around the pins, andsprings are attached to the pins to provide for instant lockup of theroller clutch. In another embodiment, the one way clutch can be of thesprag clutch type, where one or more pawls contact ratchet teeth duringlock up. The one way clutches 42 are rigidly attached to the hub shell41 using an interference fit. They can also be attached with welding,adhesive, or standard fasteners. Contacting the roller clutch pins fromthe inside of the one way clutches 42 are torque drivers 43.

The torque drivers 43 in a preferred embodiment are hardened steelcylinders with a smooth outside diameter. The outside surface of thetorque drivers 43 contact the one way clutches 42 using a tolerance sothat when torque is transferred to the one way clutches 42 they lock up,thus rotating the hub shell 41. In some embodiments, when the clutch 42a is locked up and transferring torque, the clutch 42 b is in clutchmode and freewheeling, and vice versa. The lock up mode of the clutch 42a occurs when the crank 15 a is depressed, and the clutch 42 bfreewheels as the crank 15 b is raised.

Still referring to FIG. 13, hub bearings 45 are positioned adjacent toand contact hub races 46 on each side of the hub shell 41. In apreferred embodiment, the hub bearings 45 are angular contact bearingsalthough radial bearings or thrust bearings may be used. The hubbearings 45 are constructed from individual balls, although cylindricalrollers may be used. In one embodiment, the hub bearings 45 incorporateball retainers, but individual balls or sealed cartridge bearings mayalso be used. The hub bearings 45 provide for relative movement betweenthe hub shell 41 and the drive pulleys 28, and provide radial and axialsupport to the hub shell 41. The hub bearings 45 on a second sidecontact the pulley races 47, which contact and are attached to the drivepulleys 28. A second set of bearings, the axle bearings 55, arepositioned adjacent to the drive pulleys 28, and provide radial andaxial support to the drive pulleys 28. In some embodiments the axlebearings 55 are angular contact bearings but in other embodiments, theycan be radial or thrust bearings. The axle bearings 55 on a first sidecontact the axle races 56 of the drive pulleys 28. On a second, side theaxle bearings 55 contact races on cone nuts 57. In some embodiments, thecone nuts 57 are threaded nuts which can be screwed onto correspondingthreads on the rear axle 33 and tightened up against the axle bearings55. The rear axle 33 in one embodiment is a threaded rod that definesthe longitudinal axis of the hub 40. The rear axle 33 is attached to thedropouts 63 (shown in FIG. 7) of the frame 60 using conventionalfasteners such as threaded nuts and washers.

Referring to FIGS. 13, 15, and 16, the torque drivers 43 are rigidlyattached to and rotate with the drive pulleys 28. The drive pulleys 28are positioned on each side of the hub shell 41 and are concentric withthe rear axle 33, which is also the longitudinal axis of the CVD 10. Insome embodiments, the drive pulley 28, the torque driver 43, and thepulley race 47, are constructed from the same piece, preferably hardenedsteel. However, any one of these three components can be constructedseparately, and of different materials. For example, the pulley race 47and the torque driver 43 may be constructed of a separate piece ofhardened steel and attached to the drive pulley 28, which can beconstructed of aluminum, mild steel, titanium, plastic, a composite, orany other suitable material. The drive pulley 28 is a disc shapedcomponent with an annular groove in its center to house a drive cable52.

In some embodiments each drive pulley 28 contains a spring hole 48, acable hole 49, and a clamp hole 50. The spring hole 48 provides a spacefor insertion of a first end of a return spring 51, which can bepositioned concentrically with the rear axle 33. In some embodiments,the return spring 51 is made from spring steel wire and spirals radiallyaway from the rear axle 33. The return spring 51 at a first end isattached to the drive pulley 28 via the spring hole 48. At a second endthe return spring 51 is attached to the frame 60. Attachment to theframe 60 can be made with standard fasteners or a hole can be created inthe frame 60 into which the second end of the return spring 51 can beinserted. In some embodiments the second end is the outside diameter(the larger diameter) of the return spring 51 and the first end is theinside diameter (the smaller diameter). The return spring 51 can bepositioned so that the coils decrease in diameter as the return spring51 is tensioned when a crank 15 is depressed during the power stroke. Insome embodiments the return spring 51 only needs to provide enoughtension to prevent the drive cable 52 from becoming slack on the returnstroke. In other embodiments, the return spring 51 is strong enough toreturn the crank 15 to the beginning, or top of, the stroke. Thetensioned return spring 51 rotates the drive pulley 28 in the oppositedirection that it rotates during the power stroke, returning the drivepulley to its original position, and assists in lifting the crank 15 toa position at the beginning of the stroke. The spring hole 48 isslightly larger than the material comprising the return springs 51 andis a perforation in the side of the drive pulley 28 facing away from thecenter of the hub 40.

A radially located cable hole 49 positioned at the root of a drivegroove 53 in the drive pulley 28 allows for insertion of a first end ofthe drive cable 52. In some embodiments the drive cable 52 is attachedto the drive pulley 28 with a set screw (not shown) or another suitablefastener that is threaded into a clamp hole 50. The clamp hole 50 can bea tapped hole that is located on a side of the drive pulley 28 facingaway from the center of the hub 40. The drive cable 52 is then wrappedaround the drive pulley 28 within the drive groove 53 so that the drivecable 52 wraps around itself multiple times.

The number of winds of the drive cable 52 in the drive groove 53 variesconsiderably with the application, and in the case of a human poweredvehicle, is dependent on the speed and diameter of the wheel, propeller,flywheel, or other rotating driven component. The number of winds of thedrive cable 52 is also dependent on the size and physical condition ofthe user and also the diameter of the drive pulley 28. Generally, thedrive cable 52 will have from two to six windings but in a fewapplications the drive cable 52 may be wound more than 12 revolutionsaround the drive pulley 28 and as few as ½ revolutions. In someapplications, the drive cables 52 are wound a sufficient number ofrevolutions so that there is approximately one revolution left in thedrive groove 53 when the cranks 15 are depressed and at the end of theirpower stroke. By controlling the amount of the drive cable 52 wrappedaround the drive groove 53 and leaving approximately one revolution,less tension is applied to the first end of the drive cable 52. Ifpossible, more than one revolution of the drive cable 52 should remainin the drive groove 53 so that the drive cable 52 is wrapped arounditself and friction on the sides of the drive cable 52 and at the rootof the drive groove 53 will absorb a significant amount of the tensioncreated when the drive cable 52 is pulled. In one embodiment the rootdiameter surface of the drive groove 53 is knurled or otherwiseroughened so that it grabs the drive cable 52 and distributes thetension on the drive cable 52 to a larger area, lessening the stress onthe first end of the drive cable 52.

Still referring to FIGS. 13, 15, and 16, the drive cable 52, after beingwound around the drive pulley 28, travels around the crank pulley 23(seen in FIG. 11). In one embodiment the drive cable 52 wraps around thecrank pulley 23 so that the drive cable 52 first contacts the crankpulley 23 on a forward side facing the hub 40, and it becomesdisconnected, or leaves the crank pulley 23 on a rearward side facingaway from the hub 40. In some embodiments, the drive cable 52 is routedin the opposite direction around the crank pulley 23 and the manner inwhich the drive cable 52 is wrapped around the crank pulley 23 isdependent on the desired rate of change of the stroke. The drive cable52 terminates and is attached to a cable end 54, which is constructed ofa rigid, strong material such as aluminum, steel, titanium. The cableends 54 provide for clamping of a second end of the drive cable 52 usingstandard fasteners, and are rigidly attached to the frame 60. The cableends 54 can be welded to the frame 60, fastened with machine screws,nuts, and washers, or any other suitable method. In one embodiment, thedrive cable 52 is attached to the frame 60 directly with commonfasteners and the cable ends 54 are eliminated.

Referring to FIGS. 17 and 18, as the cranks 15 a, 15 b, alternately, arepushed and returned to the beginning of their stroke, the angle at whicha crank 15 is positioned relative to a drive pulley 28 changes. Thiscreates the opportunity to vary the speed and the torque at which thedrive pulley 28 operates throughout the stroke. FIG. 17 is a schematicview of the crank 15, drive pulley 28, and drive cable 52. In FIG. 17,two positions of the crank 15 are depicted. In position A, which is thelocation of crank 15 at the beginning of a stroke, the drive cable 52 isshown attached directly to the crank 15. To make the explanation of thefollowing principle easier to understand, the crank pulley 23 is notshown. In position B, the crank 15 has rotated 10 degrees relative toposition A, which in some embodiments is approximately 33% of the lengthof the stroke. In other embodiments, the stroke length can be madelonger or shorter depending upon the size of the user, the size androtational speed of the wheel, propeller, flywheel, or other rotatingdriven component, and the diameter of the drive pulley 28. As can beseen in FIG. 17, the difference between the length of the drive cable 52in positions A and B is very small. In position B, the length of thedrive cable 52 is approximately 20% longer than in position A. In someembodiments, this results in the drive pulley 28 rotating a smallamount, and when the CVD 10 is used with a bicycle 100, produces a lowerspeed of the rear wheel 84.

Referring now to FIG. 18, positions C and D of the crank 15 aredepicted. The difference between positions C and D is again 10 degrees,or approximately 33% of the stroke length. Position D represents thecrank 15 position at the end of a stroke. It is easily seen in FIG. 18that the drive cable 52 is longer in position D than in position C. Itcan be seen by comparing FIGS. 17 and 18 that the drive cable 52 travelsover 50% farther with the same 10 degrees of movement of the crank 15 inFIG. 18 than in FIG. 17. This increase in travel of the drive cable 52increases the speed of rotation of the drive pulley 28 and the speed ofrotation of rear wheel 84. The acceleration of the rear wheel 84 changescontinuously with respect to time from the beginning of the stroke tothe end of the stroke. The continuously (over time) variable speed andtorque change can be adjusted by varying the position of the crank pivot17, the length of the crank 15, the position of drive pulley 28 relativeto crank 15, the diameter of drive pulley 28, the position and diameterof the crank pulley 23, the diameter of drive cable 52, and the lengthof the cable, among other things. Generally, when the crank 15 is at alarger angle relative to the drive cable 52, the crank 15 creates morerotation of the drive pulley 28 for an equivalent distance traveledthrough the stroke. If the crank 15 is at a small angle relative to thecable 52, the crank 15 will typically produce a small amount of rotationof the drive pulley 28 when the crank 15 is depressed during a stroke.An angle Z between the drive cable 52 and the crank 15 changescontinuously throughout the stroke and will cause changes in therotational speed of the drive pulley 28 if all other variables remainthe same. Generally, an angle Z2 of the drive cable 52 relative to thecrank 15 is greater at the end of a stroke relative to an angle Z1 atthe beginning of a stroke; this results in increased rotation of thedrive pulley 28 at the end of a stroke compared to the beginning of astroke if all other variables remain the same. The change in rotation ofthe drive pulley 28 is continuously variable.

Referring to FIG. 19, a schematic view of the position of the drivecable 52 wrapped around the drive pulley 28 at the beginning of a strokeis depicted. To make the explanation of the following principle easier,the drive pulley 28 has been hidden. It can be seen that the drive cable52 has been wound around the drive pulley 28 approximately 3.15 times.Referring to FIG. 20, a schematic view of the position of the drivecable 52 at the end of a stroke is depicted. To make the explanation ofthe following principle easier, the drive pulley 28 has been hidden. Itcan be seen that the drive cable 52 has unwound from the drive pulley 28so that the number of revolutions remaining is approximately 1.1.

At the beginning of a stroke, the drive cable 52 has a larger diameter,which decreases speed and increases torque at the drive pulley 28relative to the smaller diameter of drive cable 52 at the end of astroke. This variation in speed and torque is continuously variable,meaning that the speed and torque at the drive pulley 28 changescontinuously with respect to time throughout the stroke. The rate atwhich the speed and the torque changes can be varied and is controlledby the root diameter of the drive pulley 28, the diameter of the drivecable 52, the number of revolutions the drive cable 52 is wrapped aroundthe drive pulley 28, the length of the crank 15, the length of thestroke, and other variables.

By combining an increase in speed inherent in the change in angularposition of the crank 15 relative to the drive pulley 28, and thedecrease in diameter of the drive cable 52 during the power stroke, asignificant increase in speed can be realized at the end of the stroke.Significantly, the increase in speed is non-linear and increases rapidlytoward the end of the stroke as the rate of change, or percentage of,the decrease in the diameter of the drive cable 52 accelerates.Simultaneously, the angle of the crank 15 relative to the drive pulley28 increases the amount of drive cable 52 pulled. The combined effect ofthese two phenomena creates a seamless increase in speed throughout thestroke. This speed increase is difficult to realize on a CVD bicyclebecause the bicycle begins to accelerate rapidly, the cranks 15 becomedifficult to depress, and significantly more force is required to beapplied by the user. The amount of acceleration can be controlledthrough proper design of the CVD 10. In some embodiments, the increasein force required to reach the end of the stroke is insufficient undernormal operating conditions. This means that the cranks 15 will slowdown and stop on the power stroke before reaching the end of the strokeunless the user applies significant power. This eliminates the loss inkinetic energy at the end of each stroke.

Referring to FIG. 1, the end of the power stroke occurs when theopposite crank 15 on its return stroke contacts the frame 60. In anotherembodiment, an intermediary component (not shown) positioned between thecrank 15 and the frame 60 stops the return stroke of the crank 15. Thisintermediary component can be constructed of a resilient material suchas urethane or rubber and can be adjusted to suit the preference of theuser. The intermediary component can be attached to the frame 60 withcommon fasteners.

Referring now to FIGS. 1 and 11-13, the length and position of thestroke can be controlled by varying the length and the position of thedrive cables 52 and the dependent cable 31. The length of the dependentcable 31 can be adjusted by loosening the two machine screws that areinserted into the clamp mounts 21 of a crank 15. This loosens the forcethat the cable clamps 29 apply to the dependent cable 31. The length ofthe dependent cable 31 can then be lengthened or shortened. If thedependent cable 31 is lengthened the cranks 15 move farther away fromthe dependent pulley 24, or closer to the ground when the CVD 10 is usedin conjunction with the bicycle 100. This changes the position of theuser on the bicycle 100 and changes the speed of the bicycle 100. Whenthe cranks 15 move farther from the dependent pulley 24, the distancebetween each of the cranks 15 also increases and unwinds some of thedrive cable 52 from the drive pulleys 28. This increases the speed ratioof the CVD 10 and the bicycle 100.

The length of the drive cables 52 can be adjusted in the same manner. Ifthe fasteners attaching the drive cables 52 to the cable ends 54 areloosened, the drive cables 52 can be lengthened or shortened. If thedrive cables 52 are lengthened, the return springs 51 wind theadditional drive cable 52 onto the drive pulleys 28, decreasing speedand increasing torque to drive pulleys 28. If the drive cables 52 areshortened, speed increases and torque decreases. Thus, the user canconfigure the speed ratio of the CVD 10 to suit his or her personalpreference.

Referring now to FIGS. 21 and 22, a stroke comparison is made between atraditional rotary stroke on a bicycle and the stroke of the CVD 10.Referring to FIG. 21, a circle A depicts the stroke of a traditionalbicycle. Significantly, less than 90 degrees of a 360-degree strokeproduces power, and only about 60 degrees of the stroke efficientlyproduces power, shown by the 60-degree sign between the upper and lowerpositions X of a conventional bicycle crank. The conventional rotarystroke only becomes very efficient through about half, or 30 degrees ofthe 60-degree stroke. The arc B depicts the length of the stroke of theCVD 10, which very efficiently produces power through an approximately30 degree range. Importantly, the user's legs do not move nearly as muchas in a conventional rotary stroke, lowering stress on the knees andother joints, and reducing muscle fatigue.

Referring to FIG. 22, torque is compared between a conventional rotarystroke and the CVD 10 stroke. Increasing torque is plotted on thevertical Y axis on the left side of the graph, while the horizontal Xaxis depicts time, or the percentage of the stroke completed. The curveC denotes the torque of a conventional rotary bicycle drivetrain throughone complete stroke. As the user passes through the 60-degree portion ofthe stroke where power is produced, a significant torque spike occurs.This torque spike occurs twice per revolution, as a first leg and then asecond leg pass through the power portion of the stroke. The torque ofthe stroke drops sharply when the cranks are substantially vertical, atthe beginning and halfway through the stroke. To reduce the size of thetorque spike and to maintain momentum through the power portion of thestroke, the user must maintain a high cadence to transfer powerefficiently.

The curve D denotes the torque through the stroke of the CVD 10. Torqueis steady and level throughout the stroke because not only are thedegrees of rotation through the stroke small (between 20-40 degrees insome embodiments) and ideally configured to produce power, but alsobecause the radius of the drive cable 52 to the center of the drivepulley 28 decreases as the crank 15 moves through the power phase of thestroke. This action decreases torque. Concurrently, as the legsstraighten the leg muscles become more efficient and produce more forcetowards the end of the stroke, offsetting the decrease in distance ofthe drive cable 52 to the center of the drive pulley 28. Still referringto FIG. 22, the maximum torque produced by the CVD 10 is lower than aconventional rotary drivetrain, reducing stress on the user and the CVD10 components, but the average torque is higher. This occurs becausemuch more of the user's weight is applied to the pedals 16, due to thefact that there is no seat. Thus, the force applied to the pedals 16 ismuch greater.

Referring now to FIG. 23, an alternative CVD 110 with an independentstroke is described. For simplicity, only the differences between theCVD 110 and the CVD 10 will be discussed. The dependent cable 31 isremoved and replaced by two independent cables 131 a, 131 b, which areattached to the cranks 15 a, 15 b, respectively. At a second end, theindependent cables 131 attach to the frame 60. The independent cables131 can use common fasteners or cable clamps 29 for attachment to theframe 60. Because the dependent cable 31 is eliminated, in someembodiments the crank 15 a does not return to its original position whenthe crank 15 b is in its power stroke, and vice versa. This requiresthat a stop be implemented to end the power stroke of the CVD 110. Theindependent cables 131, which like the dependent cable 31 are flexibletension members, accomplish this purpose by becoming taut at the end ofthe power stroke. The length of the independent cables 131 can beadjusted in the same manner as the dependent cable 31. Independentpedals 116 replace the pedals 16 of CVD 10. The independent pedals 116,allow the user to pull the cranks 15 on the return stroke. In someembodiments, a cover 117, attached to the pedals 116, covers the tops ofthe user's feet. In other embodiments, the pedals 116 incorporate toeclips (not shown) so the user can pull the cranks 15. In still otherembodiments, the independent pedals 116 can be clipless pedals and theuser wears matching clipless shoes which engage and attach to hooks orother fasteners on the independent pedals 116. In still otherembodiments, the return spring 51 (shown in FIG. 11) is configured tolift the cranks 15 during the return phase of the stroke, and theindependent pedals 116 are not needed to raise the cranks.

Still referring to FIG. 23, the user can adjust the length of the strokeas with CVD 10, but can also adjust the height of the stroke by liftingthe cranks 15 higher when pedaling, which produces a slower speed and ahigher torque. The user can also depress the cranks 15 farther on thepower stroke, increasing the speed and reducing the torque. Significantratio changes in the speed and torque of the CVD 110 can be achieved inthis manner. The user can also pedal with one foot only or with bothfeet at the same time.

Referring now to FIGS. 11, 24, and 25, an alternative CVD 210 with acompound pulley 204 is disclosed. For simplicity, only the differencesbetween the CVD 210 and the CVD 10 will be described. On one side ofFIG. 24, side a, the drive pulley 28 a, crank pulley 23 a, and compoundpulley 204 a have been hidden so that the drive cable 202 a and thecompound cable 206 a are visible. On side b of FIG. 24, the drive cable202 b and the compound cable 206 b have been hidden so that compoundpulley 204 b is easily visible. The CVD 210 is similar to the CVD 10,but the CVD 210 includes compound pulleys 204 a, 204 b. In oneembodiment, the compound pulleys 204 attach to the frame 60 in the samemanner that the crank pulley 23 connects to the crank 15. The compoundpulleys 204 can be made of the same material and in the same fashion asthe drive pulleys 28. The drive cable 202 travels from the drive pulley28 to a first compound groove 208 a in compound pulley 204. The drivecable 202 wraps around a first compound groove 208 a in the compoundpulley 204 a, and the drive cable 202 fastens to the compound pulley204. Compound cable 206 wraps around a second compound groove 208 b inthe compound pulley 204 and fastens to the compound pulley 204. In someembodiments, the Compound cable 206 then wraps around the crank pulley23 before terminating at the frame 60.

Still referring to FIGS. 11, 24, and 25, the compound pulley 204increases the speed change of the CVD 210 during a stroke, as comparedto the stroke of the CVD 10. The drive cable 202 winds onto the compoundpulley 204 during a power stroke, while the compound cable 206 unwinds.This creates easy pedaling at the beginning of the power stroke, rapidlyincreasing the speed of the drive pulley 28, and thus the difficulty ofpedaling toward the end of the power stroke. The speed change can bevaried by making the first and second compound grooves 208 a, 208 bdifferent diameters, and by changing the diameter of the compound pulley204 relative to the drive pulley 28.

Referring now to FIGS. 11, 24, and 26, an alternative CVD 310 with acompound pulley 204 is disclosed. For simplicity, only the differencesbetween the CVD 310 and the CVD 10 will be described. The CVD 310substantially similar to the CVD 210, and FIG. 26 is depicted in thesame way as FIG. 24. In the CVD 310 the crank pulley 23, the idlerbearing 26, and the idler shaft 27 are not used and, rather, thecompound cable 206 attaches to the crank 15 instead of to the frame 60.Additional cable clamps 29 are used to attach the compound cable 206 tothe crank 15.

Referring now to FIG. 27, an alternative CVD 410 is disclosed. Forsimplicity, only the differences between the CVD 410 and the CVD 210will be described. The CVD 410 is substantially similar to the CVD 210,except that the CVD 410 is configured with an integral brake orgenerator 215. In some embodiments, an annular flux disc 406 is pressedonto the hub shell 41 with an interference fit. The flux disc 406 can bemade from high conducting material, such as aluminum or copper. The fluxdisc 406 has multiple annular grooves, similar to those in the compoundpulley 204. A brake 404, which can be constructed of steel, plastic, acomposite, or another suitable material, has annular protrusions whichare designed to be inserted into the space between the annular groovesof the flux disc 406. The brake 404 is designed to fasten to a frame orother rigid structure. In one embodiment, a nut (not shown) attaches tothe brake and a bolt (not shown) threads into the nut. The bolt and thenut control the position of the brake 404 relative to the flux disc 406.Brake magnets 408, which are glued or fastened with common fasteners tothe sides of the protrusions of the brake 404, fit into the spacesbetween the annular grooves of the flux disc 406 with a small amount ofclearance. When the CVD 410 is powered by a user, resistance iscontrolled by positioning the brake 404 closer or farther from the fluxdisc 406 by rotating the bolt. When the brake magnets 408 move fartherinto the flux disc 406, more resistance is created, and vice versa. Theresistance for the CVD 410 is created without any contacting parts. Thebrake magnets 408 can also be the magnets used in a permanent magnetgenerator and the flux disc 406 can be modified to become the armatureof a permanent magnet generator. In this embodiment, the resistance, orbraking, produced by the permanent magnet generator is converted toelectricity.

Referring now to FIG. 28, a scooter 500 utilizing a CVD 510 similar tothe CVD 210 is disclosed. For simplicity, only the certain features ofthe scooter 500 will be explained. In a preferred embodiment, the crankpulleys 523 are near the end of the cranks 515 (the end where the pedals517 attach to the cranks 515) to maximize the amount of travel of boththe drive cable 502 and the compound cable 506. The crank pivots 517 arelocated near the back of the rear wheel to maximize the length of thecranks 515. A cover 533, which attaches to the frame with commonfasteners or by welding, provides attachment for the compound pulleys504. In other embodiments, the compound pulleys 504 can be attached tothe frame with common fasteners. In one embodiment, the compound cable506 attaches to the cover 533, while in other embodiments the compoundcable 506 attaches to the frame 560.

Referring now to FIGS. 29 and 30, an alternative CVD 605 used on abicycle 600 is described. For simplicity, only the differences betweenthe bicycle 100 and the bicycle 600 will be described. The frame 62 ofthe bicycle 600 can be substantially similar to frame 60 of the bicycle100 but can have a frame tail 602. The frame tail 602, in oneembodiment, extends rearward and downward from the crank stay 78. At afirst end, the frame tail 602 can be attached to the frame 62 bywelding, with fasteners or adhesive, or any other suitable method toproduce a strong, rigid connection. The frame tail 602 is preferably astrong, rigid, part of the frame 62 having a hole to accept a lever stop604. The lever stop 604 in some embodiments is a hardened pin, but thelever stop 604 can also be configured as a shaft for a bearing. In someembodiments, a lever bushing 606 fits over the lever stop 604 and isheld in place by a retaining ring that is inserted into a groove in thelever stop 604 (not shown). The lever bushing 606 can be a low frictioncylindrical component that provides for relative motion between thelever stop 604 and the lever bushing 606. In other embodiments, thelever bushing 606 can be a roller bearing, such as a needle roller orradial bearing.

Still referring to FIGS. 29 and 30, a lever crank 615 can besubstantially similar to the crank 15 of bicycle 100 but can have alever pivot 612 and a lever slot 618. In some embodiments, the leverpivot 612 is a hole for receiving a lever pin 613. The lever pin 613 canbe rigidly attached to the lever crank 615 with an interference fit,welding, adhesive, or any other suitable method. The lever slot 618 ispreferably a slot formed into the lever crank 615 near the pedal 16. Insome embodiments, the lever slot 618 includes multiple notches whichallow a compound pulley shaft 620, to be secured at various locations sothat the distance between a compound pulley 622 and a lever crank pivot616 can be adjusted. The compound pulley shaft 620 can be attached tothe lever crank 615 with standard fasteners, and in one embodiment awell known quick release (not shown) is used. When the compound pulley622 is farther from the lever crank pivot 616, more of a drive cable 630and a compound cable 632 is pulled, and the bicycle 600 shifts into ahigher gear. When the compound pulley 622 is closer to the lever crankpivot 616, less drive cable 630 and compound cable 632 is pulled, andthe bicycle 600 shifts into a lower gear.

Still referring to FIGS. 29 and 30, a lever 608 is described. The lever608 attaches to the lever crank 615 with the lever pin 613, which insome embodiments is a hardened steel pin with a head. In someembodiments, a bushing or bearing (not shown) placed over the lever pin613 can be used to minimize friction between the lever 608 and the leverpin 613. In one embodiment, a hole is formed into a first end of thelever 608 to which a first lever pulley shaft 638 is rigidly attachedwith an interference fit, welding, adhesive, or any other suitablemethod. Positioned over the first lever pulley shaft 638 is a firstlever pulley 634, which is an idler pulley and is free to rotate. Insome embodiments, the first lever pulley shaft 638 has a head on one endto prevent the first lever pulley 634 from coming off the first leverpulley shaft 638. At a second end of the lever 608 is a second holewhere a second lever pulley shaft 640 is inserted using the sameattachment method as the first lever pulley shaft 638. A second leverpulley 636, which in some embodiments is substantially the same as thefirst lever pulley 634 and is also an idler pulley, is positioned overthe second lever pulley shaft 640. A guide surface 614, which is of ashape to produce the desired movement and rotation of the lever 608, isformed on one side of the lever 608 between the second lever pulley 636and the lever pivot 612. The lever bushing 606 rolls along the guidesurface 614 during a stroke. The lever bushing 606 is preferably adaptedto minimize friction and is positioned over the lever stop 604. Themovement of the lever bushing 606 forces the lever 608 to rotate in adirection that causes the compound cable 632 to wrap around the firstand second lever pulleys 634, 636. In some embodiments, the first leverpulley 634 comes contacts the compound cable 632 before the second leverpulley 636. Both the first and second lever pulleys 634, 636 increasethe amount of compound cable 632 that is pulled during the stroke. Insome embodiments, the lever 608 is configured to increase the rate ofchange of the amount of compound cable 632 pulled throughout the stroke.For example, near the beginning of a stroke, the amount of compoundcable 632 pulled during the first 5 degrees of rotation of the levercrank 615 can be one centimeter, while in the last 5 degrees of rotationof the lever crank 615 five centimeters of the compound cable 632 can bepulled. The rate of change and length of the compound cable 632 pulledduring a stroke are controlled by many variables including the distancefrom the lever pivot 612 to the crank pivot 616, the length of the lever608, the shape of the guide surface 614, the location of the lever stop604, the distance between the lever pivot 612 and the first lever pulley634, the distance between the lever pivot 612 and the second leverpulley 636, the distance between the compound pulley 622 and the crankpivot 616, the degrees of rotation of the lever crank 615 during astroke, whether a line drawn between the first lever pulley shaft 638and the second lever pulley shaft 640 is coincident with the center ofthe lever pivot 612 or is offset, and the termination point of thecompound cable 632.

Referring now to FIGS. 31-33, in some embodiments a CVD 601 using alever 608, can include a lever hook 610, which can be a generally curvedportion that forms a hook at the end of the lever 608 on the side of thesecond lever pulley 636. The lever hook 610 preferably limits therotation of the lever crank 615 during a stroke, catching the lever stop604 or lever bushing 606 and stopping the rotation of the lever crank615 at the end of a stroke. In one embodiment, the lever hook 610 can beadapted to stop the rotation of the lever crank 615 as the lever crank615 returns to the beginning of the stroke.

Referring to FIG. 31, the lever 608 is shown at the beginning of astroke. The lever hook 610 has caught on the lever bushing 606 duringthe return stroke and has prevented the lever crank 615 from swingingcloser to a drive pulley 650. It should be noted that the same returnspring 51 can be used on the CVD 601 as on the CVD 10, and the returnspring 51 is strong enough to rotate the lever crank 615 on the returnstroke back to its starting position. As the stroke begins and the levercrank 615 begins to rotate, the lever pivot 612 begins to move closer tothe lever stop 604. In some embodiments, the first lever pulley 634 isin contact with the compound cable 632.

FIG. 32 depicts the stroke midway through its power phase. The levercrank 615 is close to the lever stop 604. The lever hook 610 has movedaway from the lever stop 604, and the lever pivot 612 is closer to thelever stop 604, causing the lever 608 to rotate more rapidly, pullingmore of the compound cable 632, and thus increasing the rate of changeand accelerating the rotation of the rear wheel 84 (seen in FIG. 29).This occurs because the first lever pulley 634 pulls more of thecompound cable 632. Note that the second lever pulley 636 is about tocontact the compound cable 632.

FIG. 33 depicts the stroke at the end of its power phase. The levercrank 615 has passed the lever stop 604, and the lever bushing 606 hasrolled along the guide surface 614 until the lever bushing 606 has againcontacted the lever hook 610, stopping the lever crank 615 and endingthe power phase of the stroke. The lever 608 has rotated in the samedirection throughout the power phase of the stroke. During the returnphase of the stroke the lever 608 rotates in the reverse direction,returning to its starting position. In some embodiments, the rate ofchange and rotational speed of the drive pulley 650 continues toincrease throughout the stroke because the second lever pulley 636 hasengaged and pulled a significant amount of compound cable 632, and thedrive cable 630 has continued to lengthen.

Referring now to FIGS. 31-33, in some embodiments the acceleration ofthe drive pulley 650 increases linearly throughout the stroke. When theCVD 601 is implemented on a bicycle 600, and the user is ascending ahill, the rear wheel 84 typically rotates more slowly and pedalingbecomes more difficult. In this situation, the user is unable to exertenough force to actuate the lever cranks 615 throughout the entirestroke. Pedaling becomes too difficult toward the end of the stroke,which stops the stroke. In such a situation, the user will be pushedtoward the beginning of the stroke, where pedaling is easier. Thisaction also moves the user forward on the bicycle 600, which isadvantageous when ascending a hill. The user can choose to shorten thelength of the stroke to make pedaling easier. When the user rides down ahill, the rear wheel 84 rotates faster and the drive pulley 650 alsorotates faster to apply power to the bicycle 600. In this situation,pedaling becomes easier and the user moves farther through the strokebefore it becomes too difficult to pedal. This action also moves theuser farther back on the bicycle 600, which is advantageous whendescending a hill. To summarize, in some embodiments, the CVD 601automatically shifts the ratio to suit the needs of the user.

Referring now to FIG. 34, one embodiment of the drive pulley 650 of thebicycle 600 will be described. The drive pulley has a spiraling root 652at its root. The spiraling root 652 radius increases at a substantiallylinear rate throughout one turn, or 360 degrees of rotation. In someembodiments, the spiraling root 652 radius increases an amountsubstantially equal to the diameter of the drive cable 630 over oneturn. The drive cable 630 can have a lug 658 attached at an end thatterminates at the smallest radius of the spiraling root 652. The lug 658is a common fastener that has a flat area with a lug hole 659 to allowinsertion of a screw (not shown). The flat portion of the lug 658, whichincludes the lug hole 659, is inserted into a pulley slot 654, which isformed into the spiraling root 652. The screw in some embodiments is aflat head screw and can be inserted into a countersunk fastening hole656 which is aligned radially with the lug hole 659, so that the flathead screw is first inserted into a countersunk portion of the fasteninghole, then through the lug hole 659, then threaded into a threadedportion of the fastening hole 656.

Referring now to FIGS. 35-37, an alternative CVD 700 is disclosed. TheCVD 700 is similar to the CVD 601, using a crank 710 and a transferlever 720. At a first end, the transfer lever 720 pivots about a leverpivot 722, which can be rigidly attached to a non-moving component, suchas a frame (not shown). The components of the lever pivot 722 can besubstantially similar to the components of the lever pivot 612. A pulleyshaft 726 and a pulley 724 can be attached near a second end of thelever 720. At a first end, the crank 710 pivots about a crank pivot 712.A pedal 16 attaches to a second end of the crank 710. Also attached tothe crank 710 are a stop 714 and a bushing 716. A drive cable 730 wrapsaround a drive pulley 750. A compound cable 732 is rigidly attached to arigid, non-moving component, such as a frame (not shown).

FIG. 35 shows the CVD 700 at the beginning of the power phase of astroke or the end of the return phase of a stroke. The bushing 716contacts a guide surface 728 on the lever 720 and, as the user actuatesthe pedal 16, the crank 710 begins to move through the power phase ofthe stroke. The bushing 716 rolls on the guide surface 728. FIG. 36shows the CVD 700 midway through the power phase of a stroke. The crank710 and the bushing 716 have moved closer to the lever pivot 722, whichcauses the lever 720 to rotate more rapidly, pulling more of the drivecable 730 and the compound cable 732, which results in an increasingrate of change. FIG. 37 shows the CVD 700 at the end of the power phaseof a stroke. The crank 710 and the lever 720 are nearly parallel, andthe bushing 716 has moved closest to the lever pivot 722, which furtherincreases the rotational speed of the lever 720 and the rate of changein the amount of the compound cable 732 and the drive cable 730 pulled.The guide surface 728 can be any shape which produces the desired rateof change. For example, in some embodiments the guide surface 728 isstraight, while in other embodiments it is a curve. In still otherembodiments, the guide surface 728 is a spline or a curve produced bymultiple radii.

Passing to FIG. 38 now, it is shown a lever 609 that can be used withvarious embodiments of the CVDs previously described. The lever 609 hasgenerally flat sides 380 that terminate at a lever pivot end 381 and ata distal slider guide end 382. In one embodiment, the lever 609 includesone or more pulley attachment couplings 383, which can be holes forreceiving the shafts of the pulleys. The pulley attachment couplings 383can be located at, near, or in the vicinity of the lever pivot end 381.As illustrated in FIG. 38, in some embodiments, the lever 609 includesadditionally one or more pulley attachment couplings 384 near, at, or inthe vicinity of the slider guide end 382. It is preferable to providemultiple pulley attachment couplings 383, 384 to, among other things,allow for flexibility in choosing the location of the pulleys (notshown).

In one embodiment, the lever 609 is provided with a lever pivotattachment coupling 385, which is positioned between the lever pivot end381 and the slider guide end 382. As shown in FIG. 38, the lever pivotattachment coupling can be positioned near to the pulley attachmentcouplings 383. A mid-lever portion 386 of the lever 609, between thelever pivot attachment coupling 385 and the slider guide end 382 ispreferably provided with a curved guide surface 387. In one embodiment,the guide surface 387 defines an elliptical arc. For example, for someapplications, the guide surface 387 is characterized relative to anelliptical arc 388 having a major axis 389 of about 6-inches and a minoraxis 390 of about 3-inches. In the embodiment illustrated in FIG. 38, awidth 391 of the lever 609 can be about 1.5-inches. In some embodiments,an axis 392 collinear with the centers of the pulley attachmentcouplings 383 and the pivot lever attachment coupling 385 is located atan angle A1 of about 140-degrees relative to the major axis 389. In oneembodiment, the distance between the centers of the pulley attachmentcouplings 383 and the lever pivot attachment coupling 385 is about1-2.5-inches, and more preferably 1.5-2.0-inches. In some embodiments,the guide surface 387 transitions into a radius 393 or a radius 394,which can be, for example, a 0.75-inch radius. It should be noted thatalthough the guide surface 387 has been described in one embodiment asbeing defined by an elliptical arc, in other embodiments the guidesurface 387 can be defined by various shapes of curves, or even straightlines. For some applications, the guide surface 387 can be composed ofmultiple, sequential curves, which at least some of them can havedifferent radii.

Referring now to FIGS. 39A-39D, some physiological benefits of using aCVD are discussed. FIGS. 39A and 39B depict a user's leg position at thetop and bottom of a rotary stroke, commonly used on bicycles. FIGS. 39Cand 39D depict a user's leg position at the top and bottom of a strokewhen a CVD is used on a bicycle. FIGS. 39A-39D show a user's upper leg770, knee 772, and lower leg 774. FIG. 39A shows the distance 776between two pedals of a typical bicycle using 170 mm cranks. The totaldistance 776 between the pedals is 340 mm. FIG. 39B shows that at thebottom of a conventional rotary bicycle stroke, the user's leg isslightly bent. FIG. 39B shows the distance 777 between the bottom of auser's foot at the bottom of a conventional rotary stroke and thebottom/end of the stroke of a CVD. FIG. 39C shows that at the end of thepower phase of a CVD stroke, the user's leg is substantially straight.FIG. 39D shows the distance 778 between the pedals at the top/start andbottom/end of a CVD stroke, which is 235 mm, or 69% of the length of therotary stroke. More importantly, the user's leg is bent at an angle ofabout 91 degrees in FIG. 39D, while in FIG. 39A the user's leg is bentat an angle of about 68 degrees.

Still referring to FIG. 39, there are many physiological benefits tominimizing the amount a user must bend their legs when pedaling. Oneobvious benefit is that it is easier, because the user need not move hislegs as much or lift his legs as high. Another benefit is that there isless stress on the knees, and this is important for people with kneeproblems. Another benefit is that more muscles are used in the CVDstroke than in the conventional rotary stroke of a bicycle, and more ofan activated muscle is used. Studies have shown that stair climbing,which is analogous to the movement produced by the CVD stroke, activatesalmost all of the muscles of the lower body, including the hip flexorsand the gluteus muscles. Still another benefit of the CVD stroke is thatmuscle contractions are more efficient when muscles are lengthened orapproach lengthening rather than when they are shortened. Termedconcentric (shortening) and eccentric (lengthening) muscle contractions,eccentric muscle contractions can be far more efficient. For example,studies have shown that cycling produces muscle movement that is about15% efficient, while the muscles used in running up an incline, whichmore closely approximates the movement produced by the CVD stroke,achieve about 34% efficiency. Still another benefit of the CVD stroke isthat the users are able to switch their body weight from side to side,easily applying all of their weight to the power phase of a CVD stroke,which produces much more force than is achieved when a user is applyingforce to the pedals when seated on a bicycle.

Referencing FIG. 40 now, a bicycle 4010 that can use various embodimentsof the CVDs described here is shown. In one embodiment, the bicycle 4010includes a frame 4015 supported by a front wheel 4020 and a rear wheel4025. Top tubes 4030 extend from a head tube 4035 to a wheel axle (notshown) of the rear wheel 4025. The top tubes 4030 can be adapted toreceive and secure the wheel axle. The rear wheel 4025 is placed betweenthe top tube 4030A and the top tube 4030B. In some embodiments, a firstportion of the top tubes 4030 is actually a single tube, which thenbifurcates into two tubes as it approaches the rear wheel 4025. A downtube 4040 extends from the head tube 4035 toward a lower portion of therear wheel 4025, and is positioned generally in the same plane as thatof the rear wheel 4025 (that is, the down tube 4035 preferablyterminates in front of, and is aligned with, the rear wheel 4025). Tyingtubes 4045 are coupled to the top tubes 4030 and to the down tube 4040.For example, the tying tube 4045A is fastened at one end to the top tube4030A and at a second end to the bottom tube 4040. In some embodiments,the bottom tube 4040 is provided with an extension, or a support rod, ora shaft (not shown) for coupling the tying tubes 4045 to the down tube4040. In some embodiments, the bicycle 4010 includes a chest support4050 that is coupled to the frame 4015 by a chest support tube 4055,which is fastened to one or both of the down tubes 4030. The fasteningbetween the chest support tube 4055 and the down tubes 4030 can beadapted to allow selection of location of the chest support tube 4055along the length of the down tubes 4030. In one embodiment,reciprocating cranks 4060 can be coupled to crank pivots 4065, which canbe supported by and located near, at, or in the vicinity of, the downtube 4040 and/or the tying tubes 4045. Lever stops 4070 can be coupledthe tying tubes 4045 to provide a guiding structure for a movement of alever (not shown in FIG. 40) such as the levers 608 and 720 describedabove.

Passing to FIG. 41 now, a bicycle 4100 can include a frame 4105 thatincludes a head tube 4110 coupled to a down tube 4115. A chest support4120 can be received and/or supported on a chest support tube 4125,which couples to the down tube 4115 via a chest support tube clamp 4130.In some embodiments, the chest support tube clamp 4130 is adapted to beremovable and allow selection of location of the chest support clamp4130 a desired length of the down tube 4115. As illustrated in FIG. 41,a portion 4112 of the down tube 4115 can bend in front of, and extendtoward a lower part of, a rear wheel 4135.

In some embodiments, downstays 4140 couple the down tube 4115 to a rearwheel axle (not shown) of the bicycle 4100. In one embodiment, forexample, the downstays 4140 couple to the rear wheel axle by a bracket4145. In some embodiments, crank stays 4150 couple the downstays 4140 tothe down tube 4115. Hence, in some cases, the down tube 4115 is providedwith an extension, connecting hub, or shaft 4155 adapted to couple tothe crank stays 4150. As shown in FIG. 41, in some embodiments, thedownstays 4140 and the crank stays 4150 can be formed integrally intoone piece. The rear wheel 4135 is placed between pairs of crank stays4150 and downstays 4140.

A crank 4160, which in some embodiments is reciprocating and adapted toturn only through an angle that is less than 360 degrees, can be coupledto the down tube 4115 and/or to the crank stay 4160. In one embodiment,the crank 4160 is rotationally coupled to the connecting hub 4155. Alever stop 4165 can be attached to the crank stay 4150 to provide aguide structure to a movement of a lever (not shown in FIG. 41) such asthe levers 608 and 720 of the CVDs described above.

The foregoing description details certain inventive embodiments. It willbe appreciated, however, that no matter how detailed the foregoingappears in text, the inventions disclosed here can be practiced in manyways. It should be noted that the use of particular terminology whendescribing certain features or aspects of the inventive embodimentsshould not be taken to imply that the terminology is being redefinedherein to be restricted to including any specific characteristics of thefeatures or aspects of the invention with which that terminology isassociated.

1. A drivetrain, comprising: a crank; a pulley attached to the crank; a lever operably coupled to the crank; and a lever stop operably coupled to the lever.
 2. The drivetrain of claim 1, wherein the crank is configured to alternately move closer to and farther from the lever stop during a power phase of a stroke.
 3. The drivetrain of claim 1, wherein the crank passes by the lever stop during the power phase.
 4. The drivetrain of claim 1, wherein the lever stop is stationary relative to the crank and/or the lever.
 5. The drivetrain of claim 1, wherein the lever stop is not stationary relative to the crank and/or the lever.
 6. The drivetrain of claim 1, wherein the crank and the lever are configured such that the mechanical advantage of the power phase of a stroke decreases continually from the beginning to the end of the power phase.
 7. A drivetrain comprising: a drive pulley; a crank configured to pivot about a crank pivot; a crank pulley coupled to the crank at a location on the crank that is distal from the crank pivot, the crank pulley operably coupled to the drive pulley; a lever coupled to the crank via a lever pivot that is coupled to the crank; and a lever stop configured to guide a motion of the lever, the lever stop coupled to a structure that is stationary relative to the lever.
 8. The drivetrain of claim 7, wherein the drive pulley is coupled to a hub shell, said hub shell adapted to drive a load.
 9. The drivetrain of claim 8, wherein the drive load comprises a wheel.
 10. The drivetrain of claim 7, wherein the crank comprises lever slots adapted to facilitate selection of a location of attachment for the crank pulley.
 11. The drivetrain of claim 7, further comprising first and second lever pulleys, the first lever pulley coupled to the lever at a first end of the lever and the second lever pulley coupled to a second end of the lever.
 12. The drivetrain of claim 11, further comprising a flexible tension member coupling the drive pulley, crank pulley, first lever pulley, and second lever pulley.
 13. The drivetrain of claim 12, wherein the flexible tension member starts at the drive pulley and ends at a structure that is stationary relative to the crank.
 14. The drivetrain of claim 7, wherein the stationary structure comprises a tail that extends from dropouts of a bicycle frame.
 15. The drivetrain of claim 13, wherein the stationary structure comprises a crank stay.
 16. The drivetrain of claim 7, further comprising a second drive pulley, second crank, second crank pulley, second lever, and second lever stop.
 17. A drivetrain comprising: a crank configured to pivot about a crank pivot; a lever configured to pivot about a pivot lever; a lever stop coupled to the crank and configured to guide a motion of the lever; a drive pulley; and a lever pulley coupled to the lever and operably coupled to the drive pulley.
 18. The drivetrain of claim 17, further comprising a flexible tension member that couples the drive pulley to the lever pulley.
 19. The drivetrain of claim 17, wherein the lever comprises a guide surface upon which the lever stop operates.
 20. The drivetrain of claim 19, wherein the guide surface comprises a substantially flat surface.
 21. The drivetrain of claim 19, wherein the guide surface comprises a curved surface. 